<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title></title>
</head>
<body>
	<p class="p1 p">我是superman</p>
	<p class="p2 p">我是supertwo</p>
	<p class="p2 pp">我是superthree</p>

	<script type="text/javascript">
		let p = document.querySelector(".p2.p")
		console.log(p)

		// ppp p
		console.log(p.className)
		p.className = "ppp p"

		// ppp p pppp
		// p.className = "ppp p pppp"
		p.className += "pppp"
	</script>
</body>
</html>